Many infrastructures need anticorrosive treatment. For instance, as some steel-structured facilities such as offshore oil field drilling facilities and offshore floating docks have long-term exposure to seawater, the corrosion of such facilities are accelerated by saline matter in seawater and sun exposure. In order to extend the facilities' service life as well as to ensure security and safety, such facilities need anticorrosive treatment for their steel structures.
Currently, polytetrafluoroethylene-based (PTEF-based) coatings represent the most common anticorrosive coatings. The anticorrosive coating protects metal structures and facilities against corrosion, by seawater in most cases. However, the polytetrafluoro-ethylene resin based coating fails to meet some demanding requirements in terms of high-performance anti-corrosion and high-performance anti-erosion. The most commonly used method to measure the corrosion resistance of a coated metal substrate is the salt spray resistance test. For instance, superior anti-corrosive coatings on high-standard steel structures (such as carbon steel parts) will protect the metal from rusting for a longer period of time when undergoing the salt spray test, which equates to an extended service life and reduced maintenance costs for structures exposed to saline matter in seawater when in use. Current polytetrafluoroethylene based coatings prepared on ordinary carbon steel structures without any surface treatment can only undergo approximately 350 hrs salt spray test when the thickness of the film is 25±5 micrometer in accordance with the ASTM B-117 testing condition. Thus, it is quite difficult for such coatings to meet the increasing requirements for anticorrosion performance.
Furthermore, some bolts and nuts not only require high-performance anticorrosion, but also require the anti-corrosive coatings prepared on the bolts and nuts to have perfect anti-erosion and other mechanical performances so as to avoid coating erosion/flaking during fastening and loosing bolt-and-nut structures, insomuch that the anti-corrosion performance will not be impacted. In other words, anticorrosive coatings for steel-structures should protect the structures both from corrosion and from erosion/flaking for a longer period of time.
U.S. Pat. No. 4,139,576 (to Yoshimura, et al.) discloses a coating composition which includes a polyarylene sulfide resin, at least one imido-containing resin, and a fluorocarbon polymer. However, to date, such systems are still deficient with respect to corrosion resistance and adhesion to the substrate after exposure to seawater. Therefore, it is still necessary to develop a better anti-corrosive coating composition which not only has much better anti-corrosion performance but also has better anti-erosion performance. Furthermore, in many applications it is important that the anti-corrosion coating is effective even as a single coat application.